Sulfur-containing organosilicon compounds are useful as an essential component of silica-filled rubber compositions for the manufacture of tires. Silica-filled tires have improved performance in the automotive application, especially abrasion resistance, low rolling resistance and wet grip. Such tire performance improvements are closely related to fuel consumption savings, with great efforts being currently devoted to this end.
For fuel consumption savings, it is essential to increase the silica filling factor of rubber compositions. While silica-filled rubber compositions are effective for providing tires with reduced rolling resistance and improved wet grip, they suffer from working problems including a high green viscosity and necessary multi-stage milling. When inorganic fillers such as silica are merely compounded in rubber, the resulting rubber compositions are substantially low in breaking strength and abrasion resistance on account of short filler dispersion. Then sulfur-containing organosilicon compounds are essential for improving the dispersion of inorganic filler in rubber and chemically bonding the filler to the rubber matrix.
Of the sulfur-containing organosilicon compounds, those compounds having alkoxysilyl and polysulfide groups in the molecule, for example, bis(triethoxysilylpropyl)tetrasulfide and bis(triethoxysilylpropyl)disulfide are known effective.
Besides the above organosilicon compounds having a polysulfide group, a product obtained from transesterification reaction of a sulfide-containing organosilicon compound with an alkyl alcohol amine is known to contribute to substantial improvements in fuel consumption and abrasion resistance as disclosed in Patent Documents 12 and 13. The sulfur-containing organosilicon compounds described in these patent documents, however, are poor in shelf stability and awkward to handle.